docs: def _setup_buffer(self):
          '''
          Setup the buffer subsystem.
          '''
          if not self._buffer_cfg or not isinstance(self._buffer_cfg, dict):
              return
          buffer_name = list(self._buffer_cfg.keys())[0]
          buffer_class = napalm_logs.buffer.get_interface(buffer_name)
          log.debug('Setting up buffer interface "%s"', buffer_name)
          if 'expire_time' not in self._buffer_cfg[buffer_name]:
              self._buffer_cfg[buffer_name]['expire_time'] = CONFIG.BUFFER_EXPIRE_TIME
          self._buffer = buffer_class(**self._buffer_cfg[buffer_name])